:mod:`asyncio` -- Asynchronous I/O, event loop, coroutines and tasks
====================================================================

.. module:: asyncio
   :synopsis: Asynchronous I/O, event loop, coroutines and tasks.

.. versionadded:: 3.4

**Source code:** :source:`Lib/asyncio/`

--------------

This module provides infrastructure for writing single-threaded concurrent
code using coroutines, multiplexing I/O access over sockets and other
resources, running network clients and servers, and other related primitives.

Here is a more detailed list of the package contents:

* a pluggable :ref:`event loop <event-loop>` with various system-specific
  implementations;

* :ref:`transport <transport>` and :ref:`protocol <protocol>` abstractions
  (similar to those in `Twisted <http://twistedmatrix.com/>`_);

* concrete support for TCP, UDP, SSL, subprocess pipes, delayed calls, and
  others (some may be system-dependent);

* a Future class that mimicks the one in the :mod:`concurrent.futures` module,
  but adapted for use with the event loop;

* coroutines and tasks based on ``yield from`` (:PEP:`380`), to help write
  concurrent code in a sequential fashion;

* cancellation support for Futures and coroutines;

* :ref:`synchronization primitives <sync>` for use between coroutines in
  a single thread, mimicking those in the :mod:`threading` module;

* an interface for passing work off to a threadpool, for times when
  you absolutely, positively have to use a library that makes blocking
  I/O calls.


Disclaimer
==========

Full documentation is not yet ready; we hope to have it written
before Python 3.4 leaves beta.  Until then, the best reference is
:PEP:`3156`.  For a motivational primer on transports and protocols,
see :PEP:`3153`.

.. toctree::
   :maxdepth: 3
   :numbered:

   asyncio-eventloop.rst
   asyncio-task.rst
   asyncio-protocol.rst
   asyncio-sync.rst